When Restoring files from a Disk Safe using encryption, you will be prompted to enter the encryption passphrase. Files cannot be Restored without first entering the passphrase. The passphrase is only stored in memory and never saved to Disk or database. If the Restore Files Task is interrupted because of a CDP Server shutdown event, it will not automatically re-run. You will need to initiate a new Restore Files Task and supply the passphrase again.
Read more on this topic in Windows Control Server - Disk Safe Encryption.